A slat and coacting tie-down end piece of this general type is shown in U.S. Pat. No. 4,055,284 Bott.
In lashing the straps or other retaining members about the slat-supported articles and anchoring the same to the slat end pieces, there is a tendency to impart a force tending to rotate the end piece about the axis of the single fastening means which secures the end piece to the vehicle surface. The Bott patent would seek to avoid such end piece rotation by making the telescoping portion of his end piece of the same shape and size as the interior of his hollow slat. Several problems arise with the Bott end piece design. First, if the telescoping portion is over-size relative to the slat end, the end piece cannot be inserted in the slat. If under-size relative to the slat, the telescoping portion allows the end piece to be rotated or skewed relative to the slat. Next, and particularly when thin wall sections are utilized in the slat, a rotating force applied to the end piece can cause the side walls of the slat to be cammed or flexed outwardly by the inserted portion of the end piece and thereby to release the super-adjacent portion of an elastomeric rub strip resiliently retained in the slat groove.